The disclosed embodiment is directed generally to woodworking and more specifically to wooden corner joints and the tooling which is suitable to create wooden corner joints.
In the construction of wood frames for applications such as doors, picture frames, cabinetry, etc., rail and stile members may be used to form a wooden corner joint. The “rail” member runs horizontally and the “stile” member runs vertically, at least according to the generally accepted conventions and definitions. Typically, one member is milled or machined with one or more projections (tenons) and recesses (mortises) and the other member is milled or machined with matching tenons and mortises, only in reverse. Further, these two members are milled or machined so that the joint (the tenon of the rail into the moritise of the stile and the tenon of the stile into the mortise of the rail) defines a right angled corner joint for the article being fabricated.
While different methods or techniques can be used for the machining or milling of the desired shapes into the rail and stile, one popular approach is to use a shaper cutter. Typically these woodworking machines have relatively large (over 3 inches in diameter) individual cutters which are received by a spindle. When used for rail and stile joints, there are typically three cutters and the individual cutters are able to overlap due to their mounting on the spindle. This arrangement and the ability to overlap enables the stile edges to be radiused
Another option for milling (i.e., woodworking) a rail and stile joint is to use a router. The router receives a first router bit which is configured for the desired rail shapes (tenons and mortises) and the first portion of the corner joint is milled using the router and the selected router bit. Next, this first router bit is removed from the router and a second (matching) router bit is loaded into the router for the desired stile shapes. Since a tight and precise fit is important, these two router bits (rail and stile) are typically sold as a matched set. This means that whatever geometry might be selected, the two router bits create the tenons and mortises for that geometry where one is the reverse of the other. The orientation of each workpiece for each router bit cut (or cuts) is what determines that the joint will be a right angled corner joint. Some of the more common (matched) rail and stile geometries include ogee, shaker, round over, traditional, classical, bead and bevel. However, there are no actual restrictions on the geometry which one may select so long as the rail and stile router bits for that particular geometry are provided as a matched set so that one is the reverse of the other.
In terms of differences between using shaper cutters for a rail and stile versus using a matched router bit set, one difference is that the router bits are fixed on a shaft without the ability to overlap. Although multiple components are used in creating the stile bit, these components are secured together and fixed onto the shaft so as to create an integral unit (i.e., the stile bit). The same is true for the rail bit, although most of the components are different from those used in the stile bit.
As for the setup, the router is typically positioned beneath the worktable with the router bit extending upwardly, as shown by FIGS. 9 and 10 herein. The workpiece is positioned with the “good” side down on the upper surface of the worktable. A fence is typically used for alignment with the bearing. The thickness of the workpiece and the axial position of the stile router bit relative to the upper surface of the worktable will influence the mortise location and the tenon thickness. In the case of the rail router bit, these variables will influence the location of the tenon relative to the workpiece and the upper mortise. Importantly, all variables need to be “matched” for a precise fit of the two workpieces.
One of the requirements for the resultant wooden corner joint is that the rail and stile fit be somewhat tight and precise. Dimensions, tolerances, shapes, etc. are generally held to fairly exacting standards. As a part of these more precise shapes and exacting standards, the tenons and mortises typically have relatively sharp corners whether speaking of interior corner recesses or speaking of exterior corner edges.
One of the accepted limitations of router bit configurations for a rail and stile joint is that radiused edges on the stile are not considered to be possible or at least practical in view of the complexities and milling difficulties for the required router bit configurations.
This limitation, or at least the industry perception of this limitation, is based in part on the fact that the router bits are smaller (as compared to shaper cutters) and based in part on the fact that the bottom cutter is always attached to the shaft. As noted, the ability of the cutters to overlap is not possible with the router bits as it is with the shaper cutters.
In the milling of the rail and stile workpieces, including the resultant sharp corners (recesses and edges), all of which follows the traditional wisdom, it has been found that the wood stock being used for the desired corner joint will exhibit some chipping and splintering. If by chance this occurs in an area or region which is not visible once the joint is made, there may be fewer concerns. However, in all likelihood any chipping or splintering will be visible along the exposed edge of the stile which lays up against the interior panel of the article. Further, the joint is not considered to be as secure if there is any noticeable chipping and/or splintering of the wood stock.
The industry perception of router bit designs, and their design limitations, for a rail and stile joint is that creating radiused edges (and matching mortises) is not really a viable option. However, due to the continuing chipping and splintering issues, the radiused edge objective was the subject of additional design studies and trials resulting in the disclosed embodiment. As disclosed herein, a matched rail and stile router bit set is provided which creates a suitable edge radius as a way to try and minimize, or at least significantly reduce, any edge chipping and/or splintering problems.